Hydroxytitanium acylates in cis-conjugated diene polymer compositions and process of preparation



Fatented Oct. 3, 1961 United States Patent Ofiice GATED DIENE POLYMERCOMPOSITION D PROCESS OF PREPARATION S AN Gerard Kraus and Donald E.Carr, Bartlesville, Okla,

assignors t Phillips tion of Delaware 7 No Drawing. Filed May 1, 1958,Ser. No. 732,i16 19 Claims. (Cl. 260-4337) Petroleum Company, a corpora-This is a continuation in part of our copending United States patentapplication, Serial No. 500,279, filed April 8, 1955, now abandoned.

This invention is directed to a novel cis-conjugated d ene polymercomposition of high tensile strength and abrasion resistance. Moreparticularly, it is directed to the incorporation of hydroxytitaniumacylate into a natural rubber composition or into a syntheticcisconjugated diene polymer composition and to the improved productresulting therefrom.

Hydroxytitanium acylates, particularly hydroxytitamum stearate,hydroxytitanium cocoanut acylate, and hydroxytitaniurn soy acylate, whenemployed in natural rubber-carbon black compositions, have been found togive products which have greater abrasion resistance and, in general,improved tensile strength, particularly hot tensile strength, improvedtear tensile strength, lower heat build-up, and a higher percentage ofbound rubber than the corresponding compositions in which nohydroxytitanium acylates are present. Particularly noteworthy is theimprovement in abrasion resistance on stocks which have been aged. Wehave also found that when hydroxytitanium acylates are incorporated intocompositions comprising carbon black and synthetic cisconjugated dienepolymers such as cis-polybutadiene and cis-polyisoprene, unexpectedimprovements in tensile and hysteresis properties are realized. Theimprovements realized by the incorporation of hydroxytitanium acylatesin cis-conjugated diene polymer-carbon black compositions are notobserved in similar compositions wherein synthetic rubber of a differenttype, such as butyl rubber Or GR-S is used instead of a cis-conjugateddiene polymer.

The principal object of this invention is to provide from acis-conjugated diene polymer a rubber composition having improvedphysical properties.

A further object is the preparation of this composition by incorporatinga hydroxytitanium acylate into a natural rubber-filler composition.

Another object is to provide a synthetic rubber from cis-conjugateddiene polymer, said rubber having improved hysteresis properties.

A more specific object is the preparation of a natural rubber-carbonblack-hydroxytitanium acylate composition having certain improvedphysical properties.

Other objects, advantages and features Will be appareat to those skilledin the art from the following description and claims.

The hydroxytitanium acylates employed in this invention can berepresented by the formula where x=-100 and R represents an alkyl oralkenyl radical or a hydroXy-substituted alkyl or alkenyl radical of thetype found in cocoanut oil acids, soy oil acids, linseed oil acids, andcastor oil acids, and especially exemplified by stearic acid. Theseacids contain from 6 to 24' carbon atoms, At the lower end of this rangeare caproic, caprylic, and capric acids which contain 6, 8, and 10carbon atoms, respectively. The intermediate portion of this range isrepresented by lauric, myn'stic, and palmitic acids which contain 12,14, and 16 carbon atoms, respectively. The upper portion of the range isrepresented by stearic, oleic, linoleic, linolenic, ricinoleic, anddihydroxy stearic, all 18-carbon acids. The top of the range isexemplified by arachidic, erucic, and lignoceric acids which contain 20,22, and 24 carbons, respectively. The preferred compounds of this classare hydroxytitanium soy acylates, hydroxytitanium cocoanut acylates, andhydroxytitanium stearate per se. Com pounds of this type can be made bythe process described in US. 2,621,194.

The amount of hydroxytitanium acylate employed is generally in the rangebetween 0.5 and 10 parts by weight per 100 parts rubber, with an amountin the range from 1.5-5 parts by weight per 100 parts rubber beinggenerally preferred.

By the term cis-conjugated diene polymer as used broadly in thisdisclosure and in the claims we mean to include natural rubber as wellas the synthetic rubbers prepared from conjugated dienes having from 4to 8, inclusive, preferably 4 to 6, inclusive, carbon atoms per moleculewhich are polymerized under conditions which result in a polymer havinga high, i.e., at least percent and preferably at least percent,cis-configuration as determined by infrared analysis. Included in thisgroup of synthetic rubbers are cis polybutadiene and ci's-polyisoprene,sometimes referred to as synthetic natural rubber. Preferably thepolymer is a hydrocarbon.

Natural rubber is derived chiefly from the Hevea brasiliensis and isavailable commercially in crude form as crepe or smoked sheet.

Synthetic cis-polymers can be prepared by polymerizing a conjugateddiene or mixtures of conjugated dienes having from 4 to 8 carbon atomsin the presence of specific catalyst systems comprising an organometaland titanium tetrahalide. The conjugated dienes of the monomer systemspreferably have from 4 to 6, inclusive, carbon atoms per molecule, suchas 1,3-butadiene, 2 methy1-1,3-butadiene (isoprene),2,3-dimethyl-l,3-butadiene, 2-methyl-1,3-pentadiene and the like,although higher molecular weight monomers such as 2,3-dimethyl- 1,3pentadiene and 2 methyl 3 ethyl 1,3 pentadiene can be used. A rubberypolymer containing as high as 93 percent and higher cis-1,4-addition canbe prepared from 1,3-butadiene polymerized in the presence of a catalystcomposition comprising (a) an organometal compound corresponding to theformula R M, wherein R is an alkyl radical containing up to andincluding 12 carbon atoms, M is a metal selected from the groupconsisting of aluminum, mercury and zinc, and n is an integer equal tothe valence of the metal M, and (b) titanium tetraiodide. The contactingof the catalyst with the 1,3-butadiene preferably occurs in the presenceof a hydrocarbon diluent which does not inactivate the catalyst. Thealkyl groups can be either straight or branched chain alkyls, forexample, methyl, ethyl, propyl isopropyl, n-butyl, isobutyl, pentyl,isohexyl, n-heptyl, n-octyl, or tert-dodecyl. The alkyl groups can bethe same or difierent, such as isobutyl zinc. Examples of suitableorganometal compounds include triethylaluminum, triisobutylaluminum,dimethylrnercury, diethylmercury, diisopropylmercury, di-n-butylmercury,diisobutylrnercury, di-n-hexylmercury, di-n-dodecylmercury,dimethylzinc, diethylzinc, diisopropylzinc, di-n-bu-tylzinc,di-n-hexylzinc, di-n-octylzinc, di-n-decylzinc, and the like. Mixturesof organometal compounds can be employed in the catalyst system.

The ratio of the organometal compound to titanium tetraiodide in thecatalyst system is usually in the range of 1.0 to 50 on a mol basis,preferably 1.0 to 15. The concentration of the total catalystcomposition, i.e., organometal compound and titanium tetraiodide, isusually in the range of about 0.05 to 10 weight percent, preferably inthe range of 0.05 to weight percent, based on the total amount of1,3-butadiene charged to the polymerization reactor. The polymerizationcan be carried out at any temperature within the range of 0 to 150 C.and can also be carried out at very low temperatures, e.g. from 80 to 0C. so as to provide polymers having very high cis-1,4-configuration. Itis preferred to carry out the polymerization in the presence of ahydrocarbon diluent, although the polymerization can be carried outwithout the use of such a diluent. Depending upon the polymerizationtemperature and the particular hydrocarbon diluent used, thepolymerization can be conducted in either the liquid or the solid phase.The polymerization reaction can be carried out under autogenous pressureor any suitable pressure sufficient to maintain a reaction mixturesubstantially in the liquid and/or solid phase. The pressure will thusdepend upon the particular diluent being employed and the temperature atwhich the polymerization is conducted. The pressure in thepolymerization reactor will normally be the vapor pressure of thereaction mixture at the polymerization temperature, no outside source ofpressure being necessary. However, higher pressures can be employed, ifdesired, these pressures being obtained by some such suitable means asthe pressurization of the reactor with a gas which is inert with respectto the polymerization reaction.

Diluents suitable for use in the polymerization process are hydrocarbonswhich are not detrimental to the polymerization reaction. Suitablediluents include aromatics, such as benzene, toluene, xylene,ethylbenzene and mixtures thereof. It is also within the scope of theinvention to use straight and branched chain paraffins which contain upto and including carbon atoms per molecule. Examples of paraflins whichcan be utilized include propane, normal butane, normal pentane,isopentane, normal hexane, isohexane, 2,2,4-trimethylpentene(isooctane), normal decane, and the like. Mixtures of these parafiinichydrocarbons can also be employed as diluents in the practice of theprocess of this invention. Cycloparrafiins, such as cyclohexane,methylcyclohexane, and the like, can also be used. Furthermore, mixturesof any, of the aforementioned hydrocarbons can be used as diluents.

Cis-polyisoprene can be formed in polymerization processes similar tothose above described, using a catalyst system comprising analkylaluminum, such as triethylaluminum and triisobutylaluminum, withtitanium tetrachloride. In this polymerization system the ratio oforganometal to titanium tetrachloride should be at least 2.521 on a molbasis.

The above-described polymerization employing the catalyst systemcomprising an organometal and titanium tetrachloride can also be adaptedfor the polymerization of pentadiene and higher conjugated dienes tocis-polymers useful in our invention.

As defined above, the materials which we have found to be improved byincorporating therein a hydroxytitanium acylate are natural andsynthetic rubbery polymers having a high degree of cis-1,4configuration. By the term rubbery polymer we mean to includeelastomeric, vulcanizable polymeric material which after vulcanization,i.e., cross-linking, possesses the properties normally associated withvulcanized rubber, including materials which when compounded and curedexhibit reversible extensibility at 80 F. of over 100 percent of aspecimens original length with a retraction of at least 90 percentwithin one minute after release of the stress necessary to elongate to100 percent.

The percent of unsaturation that is cis, trans or vinyl unsaturation canbe determined by infrared spectroscopy according to any one of a numberof methods known in the art. One such method for polyisoprene andnatural rubber is described in the article of Binder and Ransaw,Analysis of Polyisoprenes by Infrared Spectroscopy, AnalyticalChemistry, 29, 503-508 (1957). The method used for determination of ciscontent of polybutadiene was as follows:

The polymer samples were dissolved in carbon disulfide to form asolution having 25 grams of polymer per liter of solution. The infraredspectrum of each of the solutions (percent transmission) was thendetermined in a commercial infrared spectrometer.

The percent of the total unsaturation present as trans 1,4- wascalculated according to the folowing equation and consistent units:

where e=extinction coeflicient (liters-mols -centimeters E=extinction(log I 1); t=path length (centimeters); and c=concentration (mols doublebond/ liter). The extinction was determined at the 10.35 micron bandusing the extinction coeflicient of 133(liters-molr -centimeters' Thepercent of the total unsaturation present as 1,2- (or vinyl) wascalculated according to the above equation, using the 11.0 micron bandand an extinction coefiicient of 184(liters-molr -centimeters- Theabsorption band maximum due to cis unsaturation varies from 13.5 micronsto 13.8 microns, depending upon the percent of trans and vinylunsaturation present. Cis unsaturation was determined by measuring thearea of the entire band between 12.0 and 15.75 microns and correctingfor the presence of the already measured trans and vinyl unsaturation.The extinction coeliicient E for cis unsaturation was determined asdescribed above except the E was determined by using the formula log (A/A), where A was the total area in the 12.00 to 15.75 micron region andA was the area of the unabsorbed portion. The extinction coefiicientthus calculated for cis unsaturation was 10.1 liters-mo1s -centimetersThe rubber compositions of this invention may be prepared in severalways. For example, the carbon black may be added to' the rubber whilethe rubber is in a dispersion, such as in a solution or in latex form oradded dry by a mill mixing procedure, using a roll mill or Banbury mill.The hydroxytitanium acylates are added along with the other compoundingingredients which include vulcanization agents such as sulfur,vulcanization accelerators, anti-oxidants, accelerator-activators, etc.Alternatively the hydroxytitanium acylate can be added in a remillingoperation subsequent to the incorporation of the other compoundingingredients. A masterbatc'n of the rubber and carbon black is preferablyprepared first and the other ingredients incorporated afterward.

Any reinforcing carbon black is applicable in these compositions, e.g.,furnace black and channel black. High abrasion and super abrasionfurnace blacks are preferred.

While this invention is not dependent upon any particular mechanism orexplanation of the action of hydroxytitanium acylates, it appears thatthese hydroxytitanium acylates produce additional linkages between thecarbon black surface and the rubber molecules. It is also possible thatthese hydroxytitanium acylates enhance the dispersion of the black inthe rubber.

One method of determining bound rubber is to extract a weighed sample ofthe rubber-carbon black composition with a suitable solvent such asbenzene. The rubber which is non-extractable is regarded as boundrubber. The presence of a hydroxytitanium acylate such ashydroxytitanium stearate in a natural rubber-carbon black compositionresults in an appreciable increase in bound rubber over a similarcomposition in which the additive is not present. A corresponding effecthas not been demonstrated in compositions of carbon black and copolymersof butadiene and styrene.

The addition of a hydroxytitaniurn acylate to a natural rubber-carbonblack composition also results in an increase in the Mooney value over asimilar composition without the hydroxytitanium acylate. A correspondingeffect has not been demonstrated in synthetic rubbercarbon blackcompositions and, therefore, appears to be specific to naturalrubber-carbon black compositions. That the carbon black is essential toan increased Mooney value may be demonstrated by determining the Mooneyvalue of a natural rubber sample, with and without a hydroxytitaniumacylate, but containing no black. There is no appreciable difference inthe Mooney values of the two compositions.

As hereinbefore stated, hydroxytitanium acylates such as hydroxytitaniumstearate, hydroxytitanium cocoanut acylate, and hydroxytitanium soyacylate, When present in natural rubber-carbon black compositions,produce certain properties which are superior to those of similarcompositions without the hydroxytitanium acylates. The abrasionresistance, particularly on the aged stocks, is greatly improved.Improvements have also been demonstrated in tensile strength and heatbuild-up. Resilience and tear tensile are also significantly improved.

These hydroxytitanium acylates, When incorporated into syntheticconjugated diene polymers having at least 80 percent cis-1,4configuration give unexpected improvements in tensile strength andhysteresis properties. This behavior of synthetic rubber compositionsfrom cis-polymers is quite surprising in view of the negative effectwhich these acylates have on tensile properties of emulsion polymerizedpolymers having low cis content, such as butyl rubber and GR-S. Emulsionpolymerization of l,3-butadiene gives a polymer with from about 60 toabout 80 percent trans 1,4-addition, from about 5 to about 20 percentcis-1,4-addition, and from about 15 to about 20 percent 1,2-addition.Sodium-catalyzed polybutadiene has from about 60 to about 75 percent1,2-addition, the remainder being cis and trans 1,4-addition. Whenpotassium and other alkali metals are employed as catalysts, the latterratios may vary to some degree, but no polybutadiene containing morethan about 35 percent of cis- 1,4 configuration has been obtained.Alfin-catalyzed polybutadiene has from about 65 to about 75 percenttrans 1,4-addition, from about 5 to about percent cis-1,4- addition, andfrom about 20 to about 25 percent 1,2-addition. For a more completediscussion of the configuration of polybutadiene, reference is made toan article by I. L. Binder appearing in Industrial and EngineeringChemistry, No. 46, 1727 (August 1954).

Since similar improvements are made in natural rubber, there is acorrelation between the benefits of our invention and the cis-1,4configuration of the polymer. Hevea rubber has been analyzed by theinfrared method and estimated to contain 97 percent polymer formed bycis-1,4-addition and 3 percent by 3,4-addition, assuming that naturalrubber is formed by polymerization of individual isoprene molecules.

Advantages of this invention are illustrated by the following examples.The reactants, and their proportions, and other specific conditions arepresented as being typical and should not be construed to limit theinvention unduly.

Example I Hydroxytitanium stearate was investigated as a compoundingingredient in super abrasion furnace black (Philblack E, a trademark ofPhillips Petroleum Company? natural rubber compositions. The followingcompounding recipe was employed:

The samples were milled, cured 30 minutes at 307 1 Physical mixturecontaining 65 percent of a complex dia rylaminaketone reaction productand 35 percent of N,N- diphenyl-p-phenylenedl amine.

2 N-cyc1ohexy1-2-benzothiazylsultenamide.

F., and physical properties determined. Results were as follows:

Hydroxytitanium stearate, parts Unaged samples:

Compression set, percent 19. 3 20. 1 20.0 21. 7 300% modu1us 1, 640 1,560 l, 710 l, 580 Tensile, p.s.i. 4, 430 4, 425 4, 400 4, 300Elongation, percent 565 585 575 585 200 F. maximum-tensile, 3, 840 4,040 3, 780 4, 500 A T, F 49.3 49. 3 47. 6 45. 9 Resilience, percent.62.1 62.0 64. 4 65.1 Mooney 49. 5 53. 5 50. 5 50.0 Bound rubber, percent1 40. 3 44. 3 44. 9 44. 7 Scorch at 250 F.:

Minimum Mooney 59. 5 60 58. 5 57. 5 Minutes to scorch 16. 5 17 15 16.5Extrusion at 195 F.:

Inches/minute 30. 1 28. 8 28 28.6 Grams/minute. 55 52 52 53 Teartensile, p.s.i. 2, 600 3, 160 3, 280 2, 820 Abrasion loss, grams 3 10.29 9. 87 9. 9. 54 Oven aged 24 hours at 212 F.:

300% modulus 1, 670 1, 740 1, 850 1, 590 Tensile, p.s.i., 80 F. 2, 5502, 510 2, 940 3, Elongation, percent" 400 410 430 480 A T, F 47.9 48.747.3 46.3 Resilience, percent 64. 7 65. 7 66. 2 67.0 Abrasion loss,grams 10. 20 9. 83 8. 98 5. 22

1 Carbon black and hydroxytitanium stearate, when used, are milled intothe rubber. The unvulcanized compositions are extracted with benzene andthe rubber that is not extractable is regarded as bound rubber. Theweight of the unextracted polymer divided by the total weight oforiginal polymer gives the percent bound rubber. The value obtained isindicative of the adsorption of rubber onto the black and also of thepromotion of reinforcement.

2 Method similar to that of Buist, Trans. Inst. Rubber Ind. 20, -172(1945). A small tensile specimen was used (ASTM, Die Size D) with a 22mil deep cut at the center of the gauge length, perpendicular to thedirection of stretch. The specimens were pulled to destruction at aspeed of 20 inches per minute on an Instron tester. The tear strengthwas computed as Tear Strength=L/w(t-d) where L is the load at break, wis the width of the specimen, 1; is the thickness, and dis the depth ofthe Cut.

3 The modified Goodyear Angle Abrasion Test was used for obtaining thesevalues; they are determined by noting the loss in weight of adoughnutshaped rubber wheel which has been subjected to the abrasiveaction of a carborundum wheel on the angle abrader for a certain lengthof time. Hence, the lower the abrasion loss, the better the rubber. Thenormal test conditions are: 15 degree angle, 33% pounds load, and 3000revolutions.

Example II Hydroxytitanium stearate was investigated as a compoundingingredient in a high abrasion furnace black (Philblack O, a trademark ofPhillips Petroleum Com pany)-natural rubber composition. Two runs weremade, one using two parts of hydroxytitanium stearate and the otheromitting the additive. In these runs 50 parts by weight of Philblack Owas used per 100 parts of natural rubber (#1 smoked sheet). Otherwisethe compounding recipe was the same as given in Example I. The stoclgswere milled, cured 30 minutes at 307 F., and physical propertiesdetermined. Results were as follows:

Hydroxytitanium stearate, parts Unaged samples:

Compression set, percent 16. 6 16. 3 300% modulus 1, 875 1, 875 Tensile,p.s.i., 80 F. 3, 890 4, 050 Elongation, percent 515 530 200 F maximumtensile, p.s.i 3, 610 3, 640 A T, F 2.6 45. 9 Resilience, percent 69.866. 7 Abrasion loss, grams 9. 46 10.20 Bound rubber, percent 1 40. 7 32.4 Scorch at 250 F.:

Minimum Mooney 56 58. 5

Minutes to scorch 16. 5 16 Extrusion at 195 F.: V

Inches/minute 37 37. 2

Grams/minute- 67. 5 69. 8 Tear tensile, p.s.i 2, 990 2, 650

Oven aged 24 hours at 212 300% modulus 1, 875 1, 750 Tensile, p.s.i 2,840 2, 090 Elongation, percent 410 340 A T F 40. 5 44. 0 Resilience,percent 72. 7 70. 2 Abrasion loss, grams- 6. 71 11.05

1 Determined as in Example I. 1 Determined as in Example I.

Example 111 Hydroxytitanium stearate, hydroxytitanium cocoanut acylate,hydroxytitanium soy acylate, hydroxytitanium castor acylate, andhydroxytitanium linseed acylate were investigated as compoundingingredients in super abrasion furnace black (Philblack E) natural rubbercompositions in which the following compounding recipe was employed:

Parts by weight Natural rubber (#1 smoked sheet) 100 Philblack P 40Hydroxytitanium acylate 0,2 Zinc mride 4 Stearic arid 3 Flexamine 1Sulfur 2 Santocur 0.5

The stocks were milled, cured 30 minutes at 307 F., and physicalproperties determined. The following results were obtained:

1 A National Bureau of Standards Abrader was employed using garnet paper(ASTM D-394-47, adopted 1940, revised 1946, 1947). higher the rating,the more abrasion-resistant the rubber.

#2% The Example IV Hydroxytitanium stearate and hydroxytitanium cocoanutacylate were investigated in Philblack O-butyl rubber compositions. Thefollowing compounding recipe was employed:

' Parts by weight Butyl rubber Philblack O 50 Zinc ox 5 Stearic i 1Sulfur 2 Methyl 'Iuads 1 Captax 1 Hydroxytitanium acylate 0,2

1 Isobutylene-isoprene copo'lymer having a molecular weight of 505,000and an unsaturation of 1.38%.

Tetramethyl thiuram disulfide.

9 2-mercaptobenzothiazole.

The following results were obtained after milling the stocks and curingthem 30 minutes at 307 F.:

Hydroxytitanium stearate was investigated as a compounding ingredient inPhilblack E-butadiene/styrene rubber compositions. Compounding waseflected in accordance with the following recipe:

Parts by weight .Butadiene/styrene rubber (GR-S) 1 100 Philblack F 40Sulfur 1.75 Zinc oxide 3 Stearic acid 1 Flexamine 1 Santocure 0.85Hydroxytitanium stearate 0,2,5

1A 71/29 butndiene/styrene rubber prepared by emulsion pglirsnerlzationat 122 F. and having a Mooney value (MLA) O The stocks were milled,cured 30 minutes at 307 F., and physical properties determined. Resultswere as follows:

A comparison of Example III (natural rubber-hydroxytitanium acylates)and Examples IV and V (synthetic rubber-hydroxytitanium acylates)illustrates the improved abrasion resistance and generally improvedtensile prop erties of the natural rubber compositions over thesynthetics.

Example VI Different quantities of hydroxytitaninm stearate wereemployed in compounding Philblack E-natural rubber compositions. Thefollowing recipe was employed:

Parts by weight Natural rubber (#1 smoked sheet). 100 Philblack F 40Zinc mride 4 Stearic acid 3 Flexamine 1 Sulfur 2 'Santocure 0.6

Hydroxytitanium stearate 0,2,5

seen-94a After mining and eerin' 'tne steers soreness alt-307 F.,physical properties were determined. Results were as follows:

Comp. 300% Elon- N BS Hydroxytitanium acylatc set. modu- Tensile,gation, abraperlu s, p.s.i. persion cent p.s.i. cent ratingHydroxytitanium stearate,

2 parts 6. 7 960 3,680 760 185 Hydroxytitanium stearate,

5 parts 7. 3 930 t 3, 640 770 173 Control (no additive) 7. 890 3, 100710 100 Note that the compositions containing hydroxytitanium stearateshowed improvement in tensile strength and abrasion resistance over asimilar composition in which no additive was included.

Example VII To determine the effect of hydroxytitaniulm stearate on theMooney value of natural and synthetic rubbercarbon black compositions,the several compositions described below (quantities expressed as partsby weight per 100 parts rubber) were prepared by mill mixing and theirMooney values determined at 212 'F. Results were as follows:

Composition: Mooney value at 212 F., MS-l' /z #1 smoked sheet PhilblackE, 40 parts 43 #1 smoked sheet Philblack E, 40 parts hydroxytitaniumstearate, 2 parts 54.5

GR-S 1 Philblack E, 40 parts 39 GR-S 1 Philblack E, 40 partshydroxytitanium stearate, 2 parts 39 1 As in Example V. 7

It is evident that the presence of hydroxytitaniuin stearate gives anappreciable increase in the Mooney value of natural rubber-carbon blackcompositions but not GR-S-carbon black rubber.

Example VIII The effect of hydroxytitanilnn stearate on the bound rubbercontent of both natural rubber and GR-S conipositions containing carbonblack was studied. Bound rubber was determined in the manner describedin Exampie 1. The compositions studied and the bound rubber content areshown below:

Composition Bound rubber,

percent #1 smoked sheet, 100 parts Philblack E, 40 parts.-- 2 37. 5 354. 7 #1 smoked sheet, 100 parts Philblack E, 40 parts hydroxytitaniumstearate, 2 parts 2 '42. 2 3 65. 1 2 28. 8 B 40. 6 GR-2, 100 partsPhilblack E, 40 parts H xy= titanium stearate, 2 parts 2 27. 8 41. 4

1 As in Example V.

2 Determined as in Example I.

3 Compositions were milled as before, heated 3 hours at 140 C. in anatmosphere of nitrogemand then extracted with benzene. The insolublepolymer was regarded as bound rubber.

Example IX Butadiene Was polymerized in the presence of atriisobutylalurninum/titaniuni tetraiodide catalyst in accordance withthe following recipei Polymerization was effected in a 20 gallonreactor. The

toluene was charged first followed by the triisobutylaluminurn,butadiene, and titanium tetraiodide, in that order, at 10 F.Polymerization temperature was held at 20 F. up to 51 percentconversionwhen it beganto in- 1 0 esieei and 36 F. at slowdown. A 67 ercentconversion was obtained in 17 hours and the polymer had a Mooney value(ML-4) of 73. The weight ratio of triisobutylaluminum/Tih was 1.34/1.The polymer solution was washed with dilute sulfuric acid to reduce theiodine and ash in the polymer. Infrared analysis for the cis, trans, andvinyl content gave the following results: cis, 94.2 percent; trans, 2.3percent; vinyl, 3.5 percent.

The eifect of hydroxytitanium stearate as a compounding ingredient insuper abrasion furnace black (Philblack E)-cis-polybutadienecompositions was investigated using the following compounding recipe:

Parts by weight Cis-polybuta'diene v I Philblack F 1 Y 40 Zinc oxide 3Stearic acid 7 a M V, 2 Resin 731 1 3 Fle XamiHe 2 1 Sulfur 1 Santocure3 1 Hydroxytitaniurn stearate 2,0

1 A 'd-isproportionated pale rosin stable to heat and light.

A physical mixture containing 65 percent of a complex diarylamineketonereaction product and 35 percent of N,N'- diphenyl-p-p11eny1enediamine.

3 N -cyclohexy1-2-benzothiazylsulfenamide,

All compounding ingredients except the hydroxytitanium stearate weremilled into the cis-polybutadiene on a roll mill, the compounded stockwas taken ofi the mill and allowed to stand an hour, and thehydroxytitanium stearate was incorporated into one portion of thecompounded stocl; during a remilling operation. The stocks were cured 45minutes at 307 F. and physical properties determined. Results were asfollows:

l The density of network chains is related to the number of crosslinkswinby the function where 'n is the number of crosslinks, 8 is thedensity of the polymer and M is the molecular weight.

The above data show tensile improvement in both the aged and unagedsamples which contained hydroxytitanium stearate. Also a surprisingdecrease in heat buildup is evident.

Example X Butadiene was polymerized using the recipe and procedure givenin Example IX. Polymerization temperature was held at 20 F. throughoutthe run. A conversion of 70 percent was reached in 20.9 hours and thepolymer had a Mooney value (ML-4) of 34. Infrared analysis gave thefollowing cis, trans, and vinyl-content: (is, 94.4 percent; trans, 2.2percent; vinyl, 3.4 percent.

The effect of variable quantities of hydroxytitanillm stearate inPhilblack E-cis-polybutadiene compositions was investigated using thefollowing compounding recipes:

The above data show that natural rubber-synthetic cispolymer blends canbe improved by the method of our invention in a manner comparable to theenhancement Recipes (partsby Weight) of natural rubber and syntheticcis-polymers individual- 1y. As shown above, the cured blend is improvedin 1 2 3 4 tensile strength and hysteresis with lower heat build-up andincreased resilience on both the aged and unaged cis-Polybutadiene 12g12g 128 a 128 stock 3 a 3 3 Example XII 2 2 2 2 a a a 3 Cis-polyrsoprenewas prepared by polymerlzation of g isoprene in accordance with thefollowing recipe:

1 1 1 1 Hydroxytitanlum stearate o 1 2 5 Parts y welghl Isoprene 100 IAs in Example IX. 7 Toluene 440 The stocks were milled and thehydroxytitanium stea- Triisobutylaluminum 1 0.495 (2.5 mmoles) rateadded as described in Example IX. They were Trlamllm lelrachlofldez 0523ITIIIIOICS) cured 30 minutes at and P y Properties 1 Charged as a 0.441molar solution in toluene. termined. The following results wereobtained; Charged as a 0.294 molar solution in toluene.

20 Polymerization was effected in bottles with the temy y itaniumstearate, perature being regulated at 30 C. A conversion of 60 partspercent was obtained in 24 hours. The polymer was 2 5 gel free and hadan inherent viscosity of 2.74. Poly- 0 1 isoprene prepared as describedabove has a cis content U d 1 25 of at least 90 percent.

5% iii riiiii/ca- 1.83 1. 84 1.80 1. 71 q Samples of the -p y p e c paqgg fi g p p 3 138 3 1 38 3 318 3 358 one with and the other withouthydroxytitanium stearate. Elongaiigmperecnt" I 79 830 850 see Compoundmsreclpes were as follows:

Shore hardness 57 57 56 A T F 41. 9 50. 7 50.3 51.7 Resilience,pcrcent71.6 71.9 73.0 73.2 Partsby wmght As shown above, the tensile strengthis increased with eisl lyi oprene 100 100 increasing amounts ofhydroxytitanium stearate with the gg gf g 2 2 most marked changeoccurring with between 1 and 2 tlearic acid a a pa ts of additive. Thespecimen containing 5 parts of s Q 5 acylate appeared to be less tightlycured. The evidence %mtligcurefgm 0.5 0.5 in improvement in resiliencetends to offset the lack of y umstemte' 0 2 improvement in heat build-upfor these samples. 1 AS in Example IX.

Exam le XI 40 p The compounded stocks were cured 30 minutes at A blendcontaimng equal parts by weight of th 307" F. and physical propertiesdetermined. Results polybutadiene described in Example X and naturalrubwere f ll her (#1 smoked sheet) was prepared and compounded inaccordance with the following formulation:

Hydroxytltanlum Parts by weight stearate, Parts Rubber blend 100Philblack F 40 2 0 Zinc oxide- 3.5

U ed les: Steanc V 4 om i i l ded Mooney (MS-11A) 29 31 Flexamme 1 13190%umOdUlli1S, p.s.l 3 3 gig Santocurc 1 1 ens BAP-5 1 E1 t t 710 650Sulfur 1.6 'i i r fi ifi fi zn g BS D e. 611 Hydroxytitamum stearate 2,0g g fi 51 62 1 As in Example-1X.- 2 1, 340 1, 320

The hydroxytitanium stearate was incorporated mm ,238 egg the rubber asin the preceding examples and the stocks were cured 45 minutes at 280 F.Results of physical tests were as follows:

As shown by the above data, cis-polyisoprene (synthetic natural rubber)is improved considerably in tensile strength on both aged and unagedstock by the addition of hydroxytitanium strearate.

The foregoing specification should be considered as illustrative of theinvention, not limiting. For example, the acylate may be incorporatedinto the rubber by means other than those described, as by treating thecarbon black with the acylate prior to the addition of the black to therubber. Such a treatment can be accomplished by immersing the carbonblack in a solution of acylate and then evaporating the solvent to leavethe acylate adsorbed on the surface of the black. Other modifications ofour invention as will be evident to those skilled in the art, can bemade, or followed, in the light of this foregoing disclosure anddiscussion, without departing from'the spirit'or. scope thereof.

We claim: a a

1. A rubber composition having improved tensile strength comprising amajor amount of sis-conjugated diene polymer selected from the groupconsisting of natural rubber and synthetic polymers of conjugated dieneshaving from 4 to 8, inclusive, carbon atoms per molecule containing atleast 80 percent cis'-1,4 addition, a minor amount of carbon black andhydroxytitanium acylate represented by the formula- Where x=-100 andeach R is selected from the grou consisting of alkyl, hydroxyalkyl,alkenyl and hydroxyalkenyl radicals and each acyl group contains 6-24carbon atoms.

3. Composition of claim 2 wherein the droxytitanium stearate.

4. Composition of claim 2 wherein hydroxytitanium salt of soy oil acids.

5. Composition of claim 2 wherein hydroxytitanium salt of coconut oilacids.

6. Composition of claim 2 wherein the acylate hydroxytitanium salt oflinseed oil acids.

'7. Composition of claim 2 wherein hydroxytitanium salt of castor oilacids.

8. A rubber composition having improved tensile strength comprising 100parts by weight of ci s-conjugated diene polymer selected from the groupconsisting of natural rubber and synthetic polymers of conjugateddiolefins having from 4 to 6, inclusive, carbon atoms per moleculecontaining at elast 90 percent cis-l,4 addition, about 40 to 50 parts byweight of carbon black, and 1.5 to parts by weight of hydroxytitaniumacylate represented by the formula acylate is hythe acylate is theacylate is the acylate is where x=5100 and each R is selected from thegroup consisting of alkyl, hydroxyalkyl, alkenyl and hydroxyalkenylradicals and each acyl group contains 6-24 carbon atoms.

9. A composition according to claim 8 wherein said carbon black isselected from the group consisting of high abrasion furnace black andsuper abrasion furnace black.

10. A rubber composition having improved tensile strength and abrasionresistance comprising a major amount of natural rubber and minor amountsof carbon 14 black and hydrexytitanium acylate represented" by theformula Where x=5-100 and each R is selected from the group consistingof alkyl, hydroxyalkyl, alkenyl and hydroxyalkenyl radicals and eachacyl group contains 6-24 carbon atoms.

11. A rubber composition having i improved tensile strength and abrasionresistance comprising a major amount of natural rubber, a minor amountof carbon black filler, and 0.5-10 parts by weight/100 parts by weightrubber of a hydroxytitanium acylate represented 'by the formula wherex=5-100 and each R is selected firom the group consisting of alkyl,hydroxyalkyl, alkenyl, and hydroxyalkenyl radicals and each acyl groupcontains 6-24 carbons.

12. A rubber composition having improved tensile strength and abrasionresistance comprising 100 parts by weight of natural rubber, 40-50 partsby weight of carbon black, and 1.5 to 5 parts by weight ofhydroxytitanium acylate represented by the formula where x=5-100 andeach R is selected from the group consisting of alkyl, hydroxyalkyl,alkenyl, and hydroxyalkenyl radicals and each acyl group contains 6-24carbon atoms.

13. A rubber composition having improved tensile strength comprising amajor amount of cis-polybutadiene containing at least percent cis-l,4addition, a minor amount of carbon black, and 0.5 to 10 parts by weightper parts of cis-polybutadiene of a hydroxytitaniu-m acylate representedby the formula Where x=5100 and each R is selected from the groupconsisting of alkyl, hydroxyalkyl, alkenyl and hydroxyalkenyl radicalsand each acyl group contains 6-24 carbon atoms.

14. A rubber composition having improved tensile strength comprising amajor amount of cis-polyisoprene containing at least 90 percent cis-1,4addition, a minor amount of carbon black, and 0.5 to 10 parts by Weightper 100 parts of cis-polyisoprene of a hydroxytitanium acylaterepresented by the formula Where x=5-100 and each R is selected from thegroup consisting of alkyl, hydroxyalkyl, alkenyl and hydroxyalkenylradicals and each acyl group contains 6-24 carbon atoms.

15. In a process for the preparation of cis-conjugated dienepolymer-carbon black compositions from rubbery material selected fromthe group consisting 'of natural rubber and synthetic polymers ofconjugated dienes having from 4 to 8, inclusive, carbon atoms permolecule containing at least 80 percent cis-1,4 addition, theimprovement comprising incorporating into the compositionhydroxytitanium acylate represented by the formula ll (I)CR where x=5100and each R is selected from the group consisting of alkyl, hydroxyalkyl,alkenyl and hydroxyalkenyl radicals and each acyl group contains 6-24carbon atoms.

16. In a process for the preparation of cis-conjugated dienepolymer-carbon black composition from rubbery material selected from thegroup consisting of natural rubber and synthetic polymers of conjugateddiolefins having from 4 to 6, inclusive, carbon atoms per moleculecontaining at least 90 percent cis-1,4 addition, the improvementcomprising incorporating into the composition hydroxytitanium acylaterepresented by the formula 1 ()-CR HO '1iO- H where x=5-l00 and each Ris selected from the group consisting of alkyl, hydroxyalkyl, alkenyland hydroxy- 16 alkenyl radicals and each acyl group contains 6'24carbon atoms.

17. Process of claim 16 wherein the composition is prepared by coatingthe carbon black with the acylate prior to the addition of the carbonblack to the rubber.

18. Process of claim 16 wherein the hydroxytitanium acylate is added toa dispersion of the rubber which is in a formselected from the groupconsisting of latex and solution in a hydrocarbon solvent.

19. In a process for the preparation of a natural rubbercarbon blackcomposition the improvement comprising incorporating into thecomposition hydroxytitanium acylate represented by the formulawherex=5-l00 and each R is selected from the group consisting of alkyl,hydroxyalkyl, alkenyl, and hydroxyalkenyl radicals and each acyl groupcontains 6-24 carbon atoms.

References Cited in the file of this patent 2 UNITED STATES PATENTS2,621,194 Ba1this Dec. 9, 1952 2,875,919 Henderson Mar. 3, 1959 FOREIGNPATENTS 1,139,418 France July 1, 1957

1. A RUBBER COMPOSITION HAVING IMPROVED TENSILE STRENGTH COMPRISING AMAJOR AMOUNT OF CIS-CONJUGATED DIENE POLYMER SELECTED FROM THE GROUPCONSISTING OF NATURAL RUBBER AND SYNETHIC POLYMERS OF CONJUGATED DIENESHAVING FROM 4 TO 8, INCLUSIVE, CARBON ATOMS PER MOLECULE CONTAINING ATLEAST 80 PERCENT CIS-1,4 ADDITION, A MINOR AMOUNT OF CARBON BLACK ANDHYDROXYTITANIUM ACYLATE REPRESENTED BY THE FORMULA